This invention is directed in general to casting molds for intraocular and contact lenses, and more particularly to a simplified casting mold construction accurately retainable in a lathe for grinding and polishing the external lens surface.
One method for making plastic intraocular and contact lenses comprises casting a liquid monomer in a mold having a cup-like structure with a convex optically defined surface, polymerizing the monomer to form a solid thereof, and grinding and polishing the surface of the solid lens material opposite the convex surface while the material is supported by the mold. In general practice, the mold containing the cast lens is mounted in a collet which is, in turn, supported in a lens generating lathe. Placement of the collet within the lathe necessitates accurate measurement to assure that the lens after grinding and polishing is of the desired finished dimensions.
In U.S. Pat. No. 4,749,530 (issued June 7, 1988 in the name of Kunzler), a mold for forming an intraocular and contact lens is shown which includes a cup-like mold cavity integrally formed with a hollow base. The base has a hemispherical external shape with a constant sized key way which follows the surface of the hemispherical base. The hemispherical base engages and mates with a guide key in a hemispherical shaped locating ring of a lens generating lathe. This patent also suggests that the base may have a finned frusto-conical base, the fins serving to position the mold in the locating ring of the lens generating lathe. In either instance, the manufacture of the lens mold with the multi-featured base is complex and requires the maintenance of tight tolerances to assure that the mold is suitably configured for receipt in the lens generating lathe.